Exercise 1.1

Express each number as a product of its prime factors:

(i) $140$

(ii) $156$

(iii) $3825$

(iv) $5005$

(v) $7429$

Find the LCM and HCF of the following pairs of integers and verify that $\text{LCM} \times \text{HCF} = \text{product of the two numbers}$.

(i) $26$ and $91$

(ii) $510$ and $92$

(iii) $336$ and $54$

Find the LCM and HCF of the following integers by applying the prime factorisation method. (i) $12, 15$ and $21$ (ii) $17, 23$ and $29$ (iii) $8, 9$ and $25$

Given that $\text{HCF}(306, 657) = 9$, find $\text{LCM}(306, 657)$.

Check whether $6^n$ can end with the digit 0 for any natural number $n$.

Explain why $7 \times 11 \times 13 + 13$ and $7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1 + 5$ are composite numbers.

There is a circular path around a sports field. Sonia takes $18$ minutes to drive one round of the field, while Ravi takes $12$ minutes for the same. Suppose they both start at the same point and at the same time, and go in the same direction. After how many minutes will they meet again at the starting point?